A method for manufacturing a radiation detection device is described in Patent Document 1. In the method described in Patent Document 1, first, a mask is disposed at a front stage of photoelectric conversion elements arrayed on an element base, and a scintillator element is formed on the photoelectric conversion elements by vapor deposition of a scintillator material by use of the mask. Next, a light reflection material is applied or vapor-deposited to the whole of the element. At this time, grooves for separating the scintillator element are filled with the light reflection material. Then, light shielding processing is applied with aluminum foil or the like, to obtain a radiation detection device.